In a new study published last week, researchers performed neuropsychological tests on 1,047 children between the ages of 7 and 10 years old and examined their exposure to thimerosal, a preservative used in many vaccines until recently, during the first 7 months of life. Researchers examined 42 separate neuropsychological outcomes and did not assess autism-spectrum disorders.
There were only a few small associations detected, and they were equally divided between positive and negative outcomes. These findings are therefore likely related to chance, and therefore the study does not find any causal association between thimerosal exposure during infancy and neurological or psychological function years later. The study is somewhat limited by the fact that it is retrospective, looking back at exposure in the past. This limits the ability to control for or to measure factors that might influence the outcome.
Thimerosal contains ethylmercury and is not related to methylmercury, the environmental toxin. Still, some have speculated whether thimerosal exposure is safe. Other studies have shown similar lack of negative outcomes. Regardless, thimerosal has been removed from almost all vaccines used in children.
